Field of the Invention
The present invention relates to a lens barrel and an optical apparatus having the same.
Description of the Related Art
There have conventionally been a variety of lens-barrel structures having a plurality of lens units movable along an optical axis for zooming and focusing, such as a cam-and-roller structure and a retractable structure in the optical axis direction. The lens barrel (or cylinder) configured to extend a moving frame that holds an optical system causes a dent on a cam and a roller for holding the moving frame when the extending moving frame receives an impact or another external force, and this dent may cause an inclination and decentering of the lens barrel and degrade the optical performance. Japanese Patent Laid-Open No. (“JP”) 2004-151279 discloses a lens barrel that includes a moving frame movable in an optical axis direction and a protective frame located on an outer circumference side of the moving frame while they are urged by an urging member so as to separate cam pins from each other, wherein the protective force receiving the external force retreats and absorbs the external force.
According to the lens barrel in JP 2004-151279, the cam pins in the moving frame and the protective frame contact one side groove surface and another side groove surface of each cam groove due to the urging member and a spring load absorbable the external force is necessary in the presence of the unsteadiness in the cam groove. However, when a spring load is made larger so as to endure the impact in a heavy lens barrel would increase the operation torque, deteriorate the durability, and cause another problem, finally degrading the optical performance.